Heat-exchange system

ABSTRACT

The invention relates to a system ( 1 ) for exchanging heat between two gaseous fluids (A, B) which are guided in channels. The inventive device has a housing-like module ( 2 ) in which an evaporator chamber ( 5 ) is separated from a condenser chamber ( 6 ) in such a way that it is gas tight. Several heat exchanger tubes ( 15 ) extend out of said evaporator chamber ( 5 ), via a test area ( 9 ) configured between the two chambers ( 5, 6 ), via the condenser chamber ( 6 ) and into an inspection chamber ( 14 ). The inspection chamber ( 14 ) is separated from the condenser chamber ( 6 ) in such a way that it is gas tight, and the heat-exchanger tubes are replaceable. The longitudinal sections ( 16 ) of the heat exchanger tubes ( 15 ) situated in the evaporator chamber ( 5 ) are protected against corrosion, whilst the longitudinal sections ( 18 ) situated in the condenser chamber ( 6 ) have fins ( 19 ).

[0001] Within the scope of U.S. Pat. No. 4,537,247, a system for the exchange of heat between two gaseous fluids guided through channels is cited as belonging to the state of the art. In this system, the heat is exchanged by heatexchanger tubes , which project into the channels from the partition wall which separates the channels carrying the fluids.

[0002] Each heat-exchanger tube has a longitudinal section which projects from the partition wall into the channel carrying the fluid with the higher temperature; these sections are covered by another tube, which leaves a gap between them. This jacket tube has an external coating of porcelain enamel. A heat-conducting material such as grease is packed into the space between the heat-exchanger tube and the jacket tube. The longitudinal sections of the heat-exchanger tubes projecting into the channels carrying the fluid to be heated are finned.

[0003] A disadvantage of the known design is that the amount of fabrication work required is significantly increased by the additional jacket tubes in the channel carrying the higher-temperature fluid. Filling the spaces between the jacket tubes and the heat-exchanger tubes with the heat-conducting material, furthermore, significantly impairs the thermal conductivity, which means that more heat-exchanger tubes must be installed to arrive at a certain heattransfer capacity, and as a result, the production cost is increased even more.

[0004] In spite of the porcelain enamel coating on the jacket tubes, it is impossible to prevent the corrosion of these tubes with absolute certainty. Once corrosion has occurred, the heat-exchanger tubes together with the jacket tubes and the heat-conducting material must be replaced, which is a very complicated operation. In this connection, additional complicating factors are that the jacket tubes are attached to the partition wall and that the areas between the jacket tubes and the heat-exchanger tubes, which contain the heat-conducting material, must be sealed off with respect to the channel carrying the fluid to be heated.

[0005] Proceeding from the state of the art, the invention is based on the task of creating a system with heat-exchanger tubes for the exchange of heat between two gaseous fluids guided through channels, which system satisfies not only the requirement for low susceptibility to corrosion in the area subject to the effects of the higher-temperature fluid, but also the requirement for simple installation or removal of the heat-exchanger tubes and especially for the easy inspection of these tubes.

[0006] This task is accomplished according to the invention by the features of claim 1.

[0007] An essential aspect of the invention is its modular construction. This makes it possible for a housing-like module with an evaporator chamber, a condenser chamber, and heat-exchanger tubes to be integrated as a single, complete unit into the adjacent channels carrying the heat-yielding fluid and the heat-absorbing fluid, regardless of whether the fluids are flowing vertically or horizontally.

[0008] Another essential aspect is the special way in which the heat-exchanger tubes are integrated into the module. The heat-exchanger tubes extend from the evaporator chamber to the condenser chamber via a test space situated between the evaporator chamber the condenser chamber and proceed from the condenser chamber to an inspection chamber, which is separated in a gas-tight manner from the condenser chamber. This design has the advantage that it is possible, by the use of the test space, to check the supports of the heat-exchanger tubes in the partition walls separating the test space from the evaporator chamber and the condenser chamber for leakage at any time, either before the system has been started up or after it has been put into operation. Thus, it is possible, for example, to fill the test space with air before the system has been started up and then to observe the air pressure in the test space. If the air pressure falls, this means a leak is present. Depending on the degree to which the pressure falls or the character of the fluids in heat exchange with each other, it is also possible, for example, to fill the test space with a barrier gas to such a pressure that in no case will any fluid pass over from one chamber to the other. It is thus impossible for any unallowable mixing of the heat-exchanging fluids, e.g., aggressive waste gas and combustion air, to occur.

[0009] Because the ends of the heat-exchanger tubes project into an inspection chamber separated in a gas-tight manner from the condenser chamber, the seal (cover) of the inspection chamber can be removed during operation and the ends checked to determine their temperature. Different temperatures mean that the heat-exchanger tubes are no longer intact. Because the heat-exchanger tubes are mounted replaceably both in the pass-through areas of the partition walls and also in the pass-through area between the condenser chamber and the inspection chamber, it is very easy to replace any individual heat-exchanger tube as needed.

[0010] The service life of the heat-exchanger tubes is also prolonged by protecting the longitudinal sections of the heat-exchanger tubes in the evaporator chamber against corrosion.

[0011] The longitudinal sections of the heat-exchanger tubes in the condenser chamber can be designed in any suitable way. The design will depend in the individual case on the character and temperature of the heat-absorbing fluid.

[0012] Thus, according to claim 2, it is possible, for example, for the longitudinal sections of the heat-exchanger tubes in the condenser chamber to be protected against corrosion also. This is advisable, for example, in cases where the fluid to be heated is also aggressive in nature.

[0013] If the longitudinal sections of the heat-exchanger tubes are corrosion-proofed, then, according to claim 3, an advantageous embodiment is to be seen in that the corrosion-proofing consists of a porcelain enamel coating. This is applied in any case directly to the external surfaces of the heat-exchanger tubes.

[0014] In the case of fluids with little or no aggressive character, it is not necessary to protect the longitudinal sections in the condenser chamber against corrosion. Depending on the heat exchange requirements, the longitudinal sections there can be either finned or hot finned according to claim 4. Fins increase the heat-exchange surface. As a result, it is possible to build a heat exchanger of the same capacity with a smaller number of heat-exchanger tubes. Thus, in spite of the fins, a system can be fabricated at lower-cost, that is, more economically.

[0015] An advantageous embodiment of the invention is provided by the features of claim 5. The module is preceded in the flow direction of the higher-temperature fluid by an additional module. A system such as this will be selected when it is possible to guarantee that the temperature of the higher-temperature fluid will always be above the dew point of sulfuric acid. In this case, the longitudinal sections of the heat-exchanger tubes in the evaporator chamber of the upstream module do not need any corrosion protection. The longitudinal sections of the heat-exchanger tubes in the condenser chamber can be finned or not finned. The two modules are connected directly to each other in the flow direction, and thus the number of heat-exchanger tubes can be effectively adapted to the heat-exchange conditions.

[0016] The heat-exchanger tubes in the upstream module also preferably project into an inspection chamber separated in a gas-tight manner from the condenser chamber. As a result, the temperature of these heat-exchanger tubes can also be monitored during the course of operation.

[0017] The heat-exchanger tubes can be supported in the partition walls separating the test space from the evaporator chamber and the condenser chamber and also in the partition wall separating the condenser chamber from the inspection chamber with the help of sealing rings, which make it possible for the heat-exchanger tubes to be installed and removed. The design according to the features of claim 6, however, can also be used effectively. In this-case, in the area of the partition wall, conical threaded collars can be welded to the circumference of the heat-exchanger tubes. At the same time that the heat-exchanger tubes are attached to the partition wall, the conicity of the thread ensures that the joint is gas-tight.

[0018] There is also the possibility of inserting the heat-exchanger tubes into the partition wall in the manner according to claim 7 by means of cylindrical or conical beads.

[0019] Especially in cases where the heat-exchanging fluids are aggressive, it can, according to the features of claim 8, be advantageous for the test space to be blocked off both against the evaporator chamber and against the condenser chamber by additional chambers filled with gas-impermeable material. This material can be, for example, a plastic or concrete.

[0020] According to claim 9, finally, it is also conceivable according to the invention that, with respect to the flow direction of the higher-temperature fluid, a washing device can be installed upstream of the longitudinal sections of the heat-exchanger tubes in the evaporator chamber. This washing device is therefore also inside the module and serves to keep the surfaces of the heat-exchanger tubes clean.

[0021] The invention is explained in greater detail below on the basis of exemplary embodiments, which are illustrated in the drawing:

[0022]FIG. 1 shows a schematic diagram in vertical cross section of a heat-exchange system according to a first embodiment;

[0023]FIG. 2 shows a schematic diagram in vertical cross section of a heat-exchange system according to a second embodiment;

[0024]FIG. 3 shows a schematic diagram in vertical cross section of a heat-exchange system according to a third embodiment;

[0025]FIG. 4 shows sector IV of FIG. 1 on an enlarged scale;

[0026]FIG. 5 shows sector V of FIG. 2 on an enlarged scale;

[0027]FIG. 6 shows a cross section of a heat-exchange system according to a fourth embodiment;

[0028]FIG. 7 shows a diagram similar to that of FIG. 4 of another embodiment.

[0029] Reference number 1 in FIG. 1 designates a heat-exchange system. System 1 comprises a housing-like module 2, which is divided transversely into two adjacent channels 3, 4. Channel 3 carries a heat-yielding fluid A in the form of hot waste gas, and channel 4 carries a heat-absorbing fluid B in the form of cold combustion air.

[0030] Module 2 has an evaporator chamber 5 and a condenser chamber 6. Evaporator chamber 5 is separated from condenser chamber 6 by two partition walls 7, 8, a certain distance apart (see also FIG. 4). Partition walls 7, 8 form the boundaries of a test space 9, which can be filled with air to a certain pressure through a fitting 10.

[0031] Condenser chamber 6 is separated by a removable bottom plate 11 from an inspection chamber 14, consisting of a fitting 12 and a cover 13.

[0032] Several heat-exchanger tubes 15 in at least one row extend out of evaporator chamber 5 and proceed via test space 9 and condenser chamber 6 to inspection chamber 14.

[0033] Longitudinal sections 16 of heat-exchanger tubes 15 located in evaporator chamber 5 are provided with a porcelain enamel coating 17 to protect them from corrosion. Longitudinal sections 18 of heat-exchanger tubes 15 in condenser chamber 6 have fins 19.

[0034] Sealing rings 20 support heat-exchanger tubes 15 in partition walls 7, 8. Heat-exchanger tubes 15 are also supported in bottom plate 11 of fitting 12 by means of similar sealing rings 20.

[0035] Fluid A (hot waste gas) flowing into evaporator chamber 5 gives up its heat to the transfer fluid in heat-exchanger tubes 15, so that a cooled fluid A1 leaves evaporator chamber 5. The heat transported by the transfer fluid in heat-exchanger tubes 15 is given up in condenser chamber 6 to cold fluid B (combustion air), so that heated fluid B1 leaves condenser chamber 6.

[0036] Test space 9 is provided so that the supports of heat-exchanger tubes 15 in partition walls 7, 8 can be checked for leaks. Thus, for example, air can be blown in through fitting 10. The air pressure is then kept under observation. If it falls, this means there is a leak.

[0037] If a leak is discovered, it is also possible to blow barrier air into test space 9 at a pressure which is higher than that of fluid A in evaporator chamber 5 and/or of fluid B in condenser chamber 6. In this way, no fluid A can pass from evaporator chamber 5 to condenser chamber 6, and no fluid B can pass from condenser chamber 6 into evaporator chamber 5.

[0038] The temperature in heat-exchanger tube 15 can be monitored through inspection chamber 14. For this purpose, cover 13 must be removed. Inspection chamber 14 is still separated by bottom plate 11 from condenser chamber 6. The free ends of heat-exchanger tubes 15 projecting into inspection chamber 14, however, are accessible, and their temperature can be checked.

[0039] In the case of system la illustrated in FIG. 2, an additional housing-like module 21 is installed immediately upstream of module 2 according to FIG. 1. This module 21 also comprises an evaporator chamber 22 and a condenser chamber 23, separated from the first chamber by a partition wall 23.

[0040] Heat-exchange tubes 25 in at least one row extend from evaporator chamber 22 via partition wall 23 and condenser chamber 24 into an inspection chamber 14 in a fitting 12, which is separated from condenser chamber 24 in a leak-tight manner by a bottom plate 11. Fitting 12 has a cover 13.

[0041] According to FIG. 5, threaded conical collars 26, which are welded to the circumference of heat-exchanger tubes 25, can be used to attach heat-exchanger tubes 25 to partition wall 23. These collars are turned into corresponding threaded bores 27 in partition wall 23.

[0042] According to the lower part of FIG. 5, however, the tubes can also be attached by conical beads 41, which are inserted into corresponding recesses 42 in partition wall 23. Cylindrical beads would also be conceivable.

[0043] Longitudinal sections 28 of heat-exchanger tubes 25 projecting into evaporator chamber 22 are not protected against corrosion, because the temperature of hot fluid A entering evaporator chamber 22 is clearly above the dew point of sulfuric acid.

[0044] Longitudinal sections 29 of heat-exchanger tubes 25 in condenser chamber 24 are finned.

[0045] Hot fluid A entering evaporator chamber 22 of module 21 heats the transfer fluid in heat-exchanger tubes 25 and the transfer fluid in heat-exchanger tubes 15 of adjacent module 2. Cooled fluid A1 emerges from evaporator chamber 5 of module 2.

[0046] The transfer fluid transports the heat to longitudinal sections 29, 18 of heat-exchanger tubes 25, 15 in condenser chambers 24, 6 of modules 21, 2, so that the cold fluid B entering condenser chamber 6 of module 2 heats up and emerges as heated fluid B1 from condenser chamber 24 of module 21.

[0047] It can be seen that the fluids are flowing vertically in FIGS. 1 and 2. For this reason, heat-exchanger tubes 15, 25 in modules 2, 21 are installed at a slight angle of 3° to the horizontal.

[0048] System 1 b illustrated in FIG. 3 is essentially the same as system 1 a in FIG. 2, except that the fluids are flowing horizontally. No further explanation is therefore required.

[0049] In the case of system 1 c shown in FIG. 6, vertical fluid streams are again present. A module 2 a corresponding to that of FIGS. 1 and 4 is integrated into channels 3, 4 carrying the fluids. In this module 2 a, heat-exchanger tubes 30, that is, longitudinal sections 31, projecting into evaporator chamber 5 a and longitudinal sections 39 projecting into condenser chamber 6 a, however, are covered over their entire length with a porcelain enamel coating 17 to protect them from corrosion.

[0050] It can also be seen that a washing device 32 is provided in evaporator chamber 5, above longitudinal sections 31 of heat-exchanger tubes 30 in this chamber. This device serves to clean the surfaces of heat-exchanger tubes 30.

[0051] Otherwise, system 1 c of FIG. 6 corresponds to that of FIG. 1, so that no further explanation is necessary.

[0052]FIG. 7 shows an embodiment which is similar to that illustrated in FIG. 4. This embodiment, however, shows not only a test space 33 with a fitting 34 but also chambers 36, filled with a gas-impermeable material 35, and tubular inlets 40, through which test space 33 can be blocked off both with respect to evaporator chamber 37 and also with respect to condenser chamber 38. Otherwise, the diagram of FIG. 7 corresponds to that of FIG. 4, so that there is no need to repeat the explanation.

[0053] List of Reference Numbers

[0054]1 system

[0055]1 a system

[0056]1 b system

[0057]1 c system

[0058]2 module

[0059]2 a module

[0060]3 channel

[0061]4 channel

[0062]5 evaporator chamber

[0063]5 a evaporator chamber

[0064]6 condenser chamber

[0065]6 a condenser chamber

[0066]7 partition wall

[0067]8 partition wall

[0068]9 test space

[0069]10 fitting

[0070]11 bottom plate

[0071]12 fitting

[0072]13 cover

[0073]14 inspection chamber

[0074]15 heat-exchanger tube

[0075]16 longitudinal sections of 15

[0076]17 porcelain enamel coating

[0077]18 longitudinal sections of 15

[0078]19 fins on 18, 29

[0079]20 sealing rings

[0080]21 module

[0081]22 evaporator chamber

[0082]23 partition wall

[0083]24 condenser chamber

[0084]25 heat-exchanger tube

[0085]26 threaded collar

[0086]27 threaded bores

[0087]28 longitudinal sections of 25

[0088]29 longitudinal sections of 25

[0089]30 heat-exchanger tube

[0090]31 longitudinal sections of 30

[0091]32 washing device

[0092]33 test space

[0093]34 fitting

[0094]35 material

[0095]36 chambers

[0096]37 evaporator chamber

[0097]38 condenser chamber

[0098]39 longitudinal sections of 30

[0099]40 tubular inlet

[0100]41 conical beads

[0101]42 recesses for 41

[0102] A hot fluid

[0103] A1 cooled fluid

[0104] B cold fluid

[0105] B1 heated fluid 

1. System for the exchange of heat between two gaseous fluids (A, B) conducted through channels, which system has an evaporator chamber (5, 5 a, 37), separated in a gas-tight manner from a condenser chamber (6, 6 a, 38) in a housing-like module, several replaceable heat-exchanger tubes (15, 30) projecting from the evaporator chamber and extending via a test space (9, 33) formed between the two chambers (6, 6 a, 38; 5, 5 a, 37) and via the condenser chamber (6, 6 a, 38) to an inspection chamber (14), separated in a gas-tight manner from the condenser chamber (6, 6 a, 38), where the longitudinal sections (16, 31) of the heat-exchanger tubes (15, 30) in the evaporator chamber (5, 5 a, 37) are protected against corrosion.
 2. System according to claim 1, characterized in that the longitudinal sections (39) of the heat-exchanger tubes (30) in the condenser chamber (6 a) are protected against corrosion.
 3. System according to claim 1 or claim 2, characterized in that the corrosion protection consists of a porcelain enamel coating (17).
 4. System according to claim 1, characterized in that the longitudinal sections (18) of the heat-exchanger tubes (15) in the condenser chamber (6) are finned.
 5. System according to one of claims 1-4, characterized in that the module (2) is preceded in the flow direction of the higher-temperature fluid A by an additional housing-like module (21) with an evaporator chamber (22), a condenser chamber (24), and heat-exchanger tubes (25), in which additional module the longitudinal sections (28) of the heat-exchanger tubes (25) in the evaporator chamber (22) do not have corrosion protection.
 6. System according to one of claims 1-5, characterized in that the heat-exchanger tubes (15, 25, 30) are screwed in a gas-tight manner from the side of the condenser chamber (6, 6 a, 24) into the partition wall (7, 23) separating the condenser chamber (6, 6 a, 24) from the evaporator chamber (5, 5 a, 22) or from the test space (9, 33) by means of a conical, threaded collar (26).
 7. System according to one of claims 1-5, characterized in that the heat-exchanger tubes (15, 25, 30) are fitted in a gas-tight manner by means of a cylindrical or conical bead (41) into a complementary recess (42) in the partition wall (7, 23) separating the condenser chamber (6, 6 a, 24) from the evaporator chamber (5, 5 a, 22).
 8. System according to one of claims 1-7, characterized in that the test space (33) is blocked off both against the evaporator chamber (37) and against the condenser chamber (38) by chambers (36) filled with a gas-impermeable material (35).
 9. System according to one of claims 1-8, characterized in that the longitudinal sections (31) of the heat-exchanger tubes (30) in the evaporator chamber (5 a) are preceded in the flow direction of the higher-temperature fluid (A) by a washing device (32). 